WO2007083681A1

WO2007083681A1 - Method of solubilizing carbon nanomaterial

Info

Publication number: WO2007083681A1
Application number: PCT/JP2007/050649
Authority: WO
Inventors: Junya Suehiro; Kiminobu Imasaka
Original assignee: Kyushu University, National University Corporation
Priority date: 2006-01-20
Filing date: 2007-01-18
Publication date: 2007-07-26
Also published as: US8048275B2; US20090250333A1; JPWO2007083681A1; JP4752073B2

Abstract

[PROBLEMS] To provide a method of solubilizing a carbon nanomaterial, in which carbon nanomaterials without structural deterioration can be dissolved in hydrophilic solvents easily and uniformly, and in which the dispersibility thereof can be maintained for a prolonged period of time, and in which the solubilizing treatment can be performed at low cost and control of the treatment is easy. [MEANS FOR SOLVING PROBLEMS] There is provided a method of solubilizing a carbon nanomaterial, characterized mainly in that a carbon nanomaterial is mixed in a hydrophilic solvent and streamer discharge is carried out in the hydrophilic solvent so that the carbon nanomaterial is dissolved in the hydrophilic solvent with the state of dispersion thereof stably maintained.

Description

Specification

Solubilization method of bonbon nanomaterial

Technical field

[0001] The present invention relates to a method for dissolving a carbon nanomaterial such as carbon nanotube (hereinafter referred to as CNT) or fullerene in a hydrophilic solvent such as water or alcohol.

Background art

In recent years, nanotechnology has made rapid progress. Above all, CNTs are attracting attention because they have excellent characteristics. In other words, CNTs are excellent in electrical characteristics, mechanical strength, etc., and there is great expectation as a filler constituting composite materials from organic semiconductors, etc., and applications to electronic devices and electrochemistry will be limited in the future. It is not expected. In addition, since CNT has a size (diameter) of several nanometers, it is a means of transporting medical components such as probes and other medical components such as anti-cancer drugs and anti-viruses into the living body. As a cosmetic ingredient, expectations are growing. The same applies to fullerenes such as C60 and C70, carbon nanohorns, and carbon nanocapsules. The CNTs, fullerenes, and carbon nanocapsules mentioned here contain carbon clusters that are partially substituted with hetero atoms or encapsulated with hetero atoms in addition to pure carbon clusters.

However, CNTs, carbon nanohorns, fullerenes and the like have the property that they are hardly soluble in hydrophilic solvents such as water and organic solvents (alcohol, acetic acid, etc.), despite these excellent properties. ing. Even in CNTs, single-walled carbon nanotubes (SWCNT) are much more sparingly soluble than multi-walled carbon nanotubes (MWCNT). The same applies to single-walled carbon nanophones (SWCNH). And this property hinders the expansion of its use, contrary to the great expectations for carbon nanomaterials.

That is, a hydrophilic solvent such as water is highly hydrophilic and easily dissolves a highly hydrophilic polar solute, but carbon nanomaterials such as CNT and fullerene are nonpolar (hydrophobic). It is difficult to dissolve. For this reason, chemical treatment such as acid treatment has been applied to the surface of CNT and fullerene. Applied to the surface to form a carboxy group on the surface, and a physical adsorption method in which a solubilizing agent such as a surfactant is physically adsorbed on the surfaces of CNTs and fullerenes. (For example, Patent Documents 1 and 2). In the physical adsorption method, ultrasonic vibration or the like is often added after the addition of the solubilizing agent in order to promote solubilization. Unlike the above-described chemical adsorption method, such a physical adsorption method has a feature that structural defects are rarely formed on the CNT surface. Here, the hydrophilic solvent is a solvent having a hydrophilic group and a high dielectric constant.

[0005] By the way, although there is no direct relationship with this soluble soot treatment, the present inventors have previously proposed a high-voltage pulsed arc discharge method in water as an efficient method for producing carbon nanoparticles (non- Patent Document 1). In this research, the present inventors have found that carbon nanoparticles produced by the production method of Non-Patent Document 1 are produced in a state of being uniformly dispersed in water.

[0006] However, the production method reported in Non-Patent Document 1 is an epoch-making method that achieves the production of carbon nanoparticles and soluble properties at once by pulsed arc discharge in water. Dispersion that occurs at this time is incidental to the production of carbon nanoparticles, and is a general soluble solvent that dissolves carbon nanomaterials produced by any production method in a hydrophilic solvent. It wasn't the way. In addition, the high-voltage pulse arc discharge method used here is basically compatible with the treatment in gas because it uses thermal plasma, requires high energy, and the device is also simple. It was difficult.

[0007] Here, as used herein, "solubilization" means that the solvent is dissolved in a hydrophilic solvent! /, And a hydrophobic property is partially imparted with a hydrophilic property. It means that this solute is dispersed inside. Therefore, “solubilization” as used in this specification does not mean a state of no turbidity corresponding to emulsion (emulsification), but dissolves and disperses difficultly soluble solutes (forms turbidity as normal). Is equivalent to a combination of

[0008] Now, the thermal plasma is not used as in the pulse arc discharge of Non-Patent Document 1. A low-temperature plasma (non-equilibrium plasma) such as oxygen or nitrogen gas is used, and the multilayer CNT is plasma-treated in the air. Thus, a dispersion method has been proposed in which the content of acidic functional groups with respect to carbon on the surface is set to 2% or more and is dispersed in a liquid using ultrasonic waves or the like (for example, Patent Document 3). Since this method uses low-temperature plasma, the discharge device is a high-voltage pulsed arc discharge method. It will be easier than.

[0009] In Patent Document 3, the reason why multilayer CNTs can be dispersed is that acidic functional groups exist on the surface of multilayer CNTs, so that acidic functional groups of other multilayer CNTs adjacent to each other in liquid can be separated from each other. There is a hypothesis that the multi-walled CNTs that have become repelled and intertwined are loosened and dispersed. However, plasma treatment is performed in the above specific gas atmosphere so that the content of acidic functional groups is 2% or more, and then physical dispersion treatment such as ultrasonic wave and high-speed stirring is performed in the liquid. The number of processes increases and the process becomes complicated, the process becomes time consuming, and the equipment becomes heavy and the control and management becomes difficult, resulting in high costs. Met.

[0010] As described above, the conventional plasma treatment for modifying the surface of the CNT utilizes discharge in a gas atmosphere, but the discharge occurs not only in the gas atmosphere but also in water. This is as reported by the present inventors in the carbon nanoparticle production method of Non-Patent Document 1.

[0011] And it has been reported that radicals such as OH radicals, H radicals, O radicals, H 2 O, and ozone O are generated when pulse streamer discharge is performed in water (for example,

2 2 3

Non-patent literature 2, 3). Also, it is reported that the discharge plasma force emits strong ultraviolet rays corresponding to about 30% of its energy, and the vicinity along the discharge channel is activated, and the generated HO is decomposed into OH radicals by the ultraviolet rays. (Non-patent

twenty two

Reference 2). However, these pulse streamer discharges reported in Non-Patent Documents 2 and 3 form radicals in water and treat the microorganisms and harmful chemicals in water by their activated action. One of the physical properties of a material in a hydrophilic solvent, that is, the problem of changing a sparingly soluble property to a soluble property, and a solution to the problem (solubility for dissolving carbon nanomaterials in a hydrophilic solvent) It is unrelated to (method). In addition, for example, there is a wastewater treatment device that uses an underwater streamer discharge for the water purification as described above (for example, Patent Document 4).

[0012] Furthermore, it has been reported that when gas publishing is performed when performing pulse streamer discharge in water, not only a physical effect but also a direct chemical effect is generated to generate radicals ( Non-patent document 4). According to Non-Patent Document 4, when the gas publishing gas is oxygen, a considerable amount of OH radicals are generated, and in the case of argon, there are many H radicals and O radicals. The amount of H radicals produced is small. However, Non-Patent Document 4, as well as Non-Patent Documents 2 and 3, does not suggest a soluble solution method for dissolving carbon nanomaterials in a hydrophilic solvent. In other words, what contribution can be made using streamer discharge in a solvent to dissolve carbon nanomaterials is currently unknown.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-12310

Patent Document 2: Japanese Patent Laid-Open No. 2001-104771

Patent Document 3: Japanese Patent Laid-Open No. 2003-300715

Patent Document 4: JP 2001-252665 A

Special Reference 1: J.buehiro, K.Imasaka, Y.Ohshiro, u.Zhou, M.Hara, N.bano ^ Production of.carbon nanoparticles using pulsed arc discharge triggerd by dielectric breakdown ι n water ", Japan Journal.Applied Physics, 42 卷, 2003, p. 1483— p. 1485 f ^^ j¾2: B. Sun, M. Sato, JSClements ^ "Non-uniform pulse discharge- induced radical product in distilled water", Journal. Electrostatics ^ 43 Tsuji, 1998, p. 115 -p. 126

Patent Document 3: H. Akiyama, “Streamer discharge in liquid and their applications,”, IEE ETrans.Electr.Insl., 39 卷, 2000, p. 646—p. 652

f ^^ j¾4: B.Sun, M.Sato, JSClements ^ "Optical study of active species puroduc ed bya pulsed streamer corona discharge in water", Journal. Electrostatics ^ 39 卷, 1 997, p. 189—p. 202

Disclosure of the invention

Problems to be solved by the invention

[0014] As described above, carbon nanomaterials such as CNT, carbon nanohorn, and fullerene have the property of being insoluble in hydrophilic solvents. For this reason, chemical bonding methods and physical adsorption methods using surfactants are performed. However, the chemical bonding method damages the structure of the carbon nanomaterial, leading to structural deterioration of the carbon nanomaterial, and the physical adsorption method requires delicate processing such as controlling the concentration of the solubilizing agent. There are many, it is difficult to control the process stably.

[0015] Further, the inventors of the present invention have developed a carbon nanotube produced by high-voltage pulse arc discharge in water. It was discovered that nanoparticles dispersed uniformly in water, but this dispersion occurred in the process of carbon nanoparticle production. Carbon nanomaterials produced by other production methods were dissolved in a hydrophilic solvent. In addition, the dispersibility of the particles obtained by this high-voltage pulsed arc discharge can be further improved, and it is suitable for general long-term storage of existing carbon nanomaterials produced by various other methods. It was difficult to say that this was an optimal dispersion method.

[0016] The dispersion method of Patent Document 3 is a plasma treatment in the air to control the ratio of acidic functional groups, and then the dispersion is dispersed in the liquid. Therefore, the treatment is complicated, requires time, and is expensive. It was difficult to control. In addition, the underwater pulse streamer discharge reported in Non-Patent Document 3 and Patent Document 4 uses OH radicals to treat microorganisms and harmful chemicals in water. What is the solubility method for carbon nanomaterials? Unrelated.

[0017] Further, Non-Patent Document 4 discloses that when performing gas publishing when performing pulse streamer discharge in water, radicals are generated not only by physical action but also by direct chemical action. To do. However, this is only for treating microorganisms and harmful chemical substances by the activity of radicals, and does not suggest the problem and method of the solubility of poorly soluble carbon nanomaterials. In short, the problem of solving only one property, that is, the hardly soluble property, into a soluble property without changing the structure of the carbon nanomaterial (without causing structural deterioration) is described in Patent Literature. It is not disclosed in 1-4 and Non-Patent Documents 1-4.

[0018] In the future, carbon nanomaterials are expected to be applied in many fields such as electronic devices and electrochemistry, and are also included in the fields of medicines and medical ingredients in the medical and pharmaceutical fields, as well as in daily products such as cosmetics. There is great expectation as a means of transporting components into the living body. The carbon nanomaterial solubility technology is an indispensable technology for these technologies, and the development of a technology for easily and uniformly solubilizing the carbon nanomaterial in a hydrophilic solvent is desired.

Therefore, the present invention can easily and uniformly dissolve a carbon nanomaterial in a hydrophilic solvent without causing structural deterioration, can stably maintain dispersibility over a long period of time, and can be solubilized. Carbon nanomaterials that can be processed at low cost and can be easily controlled An object of the present invention is to provide a solubilization method.

Means for solving the problem

[0020] The method for soluble carbon nanomaterials of the present invention involves mixing carbon nanomaterials in a hydrophilic solvent and repeatedly performing streamer discharge in the hydrophilic solvent to bond OH groups to the surface of the carbon nanomaterial. The main purpose is to generate radicals derived from a solvent that can be dissolved in the solvent, to make the carbon nanomaterial hydrophilic with the radicals so that it can be dissolved in the solvent, and to be stably dispersed in the hydrophilic solvent. Features.

The invention's effect

[0021] According to the method for dissolving carbon nanomaterials of the present invention, the carbon nanomaterial can be easily and uniformly dissolved in a hydrophilic solvent without causing structural deterioration, and is stable over a long period of time. Thus, dispersibility can be maintained, and soluble solubilization can be performed at low cost, and processing can be easily controlled.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] The first embodiment of the present invention is a solvent in which a carbon nanomaterial is mixed in a hydrophilic solvent, and a streamer discharge is repeatedly performed in the hydrophilic solvent to bond an OH group to the surface of the carbon nanomaterial. A carbon nanomaterial characterized in that a radical derived therefrom is generated in the solvent, and the carbon nanomaterial is hydrophilized with the radical to be soluble in the solvent and stably dispersed in the hydrophilic solvent. This method can easily and uniformly dissolve carbon nanomaterials in a hydrophilic solvent without structural deterioration, and can maintain dispersibility over a long period of time.匕 Processing can be performed at low cost, and processing control can be facilitated.

[0023] A second form of the present invention is a form dependent on the first form, wherein the streamer discharge is a pulse streamer discharge. An extremely simple apparatus can be used for the treatment, the carbon nanomaterial can be easily dissolved in a hydrophilic solvent, and the dispersibility can be stably maintained over a long period of time.

[0024] A third form of the present invention is a form subordinate to the first or second form, wherein the streamer discharge mainly generates H radicals and O radicals in the hydrophilic solvent, and is in the hydrophilic solvent. Of carbon nanomaterials characterized by the formation of OH groups in carbon nanomaterials The carbon nanomaterial can be easily, uniformly and easily dissolved in a hydrophilic solvent without deteriorating the structure of the carbon nanomaterial, and the dispersibility can be stably maintained over a long period of time.

[0025] A fourth form of the present invention is a form dependent on the first or second form, wherein the streamer discharge mainly generates OH radicals in the hydrophilic solvent, and the carbon nano-particles in the hydrophilic solvent. This is a carbon nanomaterial solubilization method characterized by forming OH groups in the material. The carbon nanomaterial can be easily, uniformly and easily dissolved in a hydrophilic solvent without causing structural deterioration. Dispersibility can be stably maintained over a period of time.

[0026] A fifth form of the present invention is a form subordinate to the first or second form, wherein a shock wave and / or an ultrasonic wave is a hydrophilic property during the discharge as a spontaneous or other physical force by the discharge. This is a method for dissolving carbon nanomaterials, which is characterized by being able to cover carbon nanomaterials in a solvent, and allows carbon nanomaterials to be easily and quickly dissolved in hydrophilic solvents by the synergistic action of radicals and physical forces. be able to.

[0027] A sixth aspect of the present invention is a form dependent on the first or second aspect, wherein the carbon nanomaterial is any one of multi-walled carbon nanotubes, single-walled carbon nanotubes, fullerenes, and carbon nanocapsules. This is a method for soluble carbon nanomaterials, which can be used for various applications by dissolving various carbon nanomaterials.

[0028] A seventh form of the present invention is a form dependent on the first or second form, wherein a streamer discharge is applied between electrodes at a predetermined frequency with a pulse voltage of a pulse width of 10 ns or more and 1 μs or less. This is a method for dissolving a carbon nanomaterial, characterized in that it generates radicals in a hydrophilic solvent, and the hydrophilic property is ensured by making the carbon nanomaterial hydrophilic without causing structural deterioration. It can be dissolved easily and uniformly, dispersibility can be maintained over a long period of time, soluble soot treatment can be performed at low cost, and control of the treatment can be facilitated.

[0029] In the eighth embodiment of the present invention, carbon nanomaterials are mixed in a hydrophilic solvent, and streamer discharge is repeatedly performed while publishing a gas in the hydrophilic solvent, thereby binding a base to the surface of the carbon nanomaterial. A radical derived from a solvent that can be generated is generated in the solvent, and the carbon nanomaterial is hydrophilized with the radical so that it can be dissolved in the solvent. It is a soluble method for carbon nanomaterials characterized by being stably dispersed in a medium, and it is easy to make single-walled carbon nanotubes or single-walled carbon because streamer discharge is performed while publishing gas in suspension. A hardly soluble carbon nanomaterial such as a nanohorn can be dissolved in a hydrophilic solvent, and the dispersibility of the carbon nanomaterial can be stably maintained over a long period of time. In addition, it is possible to realize soluble properties that do not cause structural deterioration of the carbon nanomaterial, and it is possible to improve only dispersibility.

[0030] A ninth form of the present invention is a form subordinate to the eighth form, wherein the gas is any one of oxygen, ozone, or an inert gas. This method can effectively dissolve poorly soluble carbon nanomaterials such as SWCNT and SWCNH in hydrophilic solvents, and the dispersibility of carbon nanomaterials can be maintained stably over a long period of time. be able to.

[0031] In the tenth aspect of the present invention, a carbon nanomaterial is mixed in a hydrophilic solvent in which hydrogen peroxide or ozone is dissolved, and a streamer discharge is repeatedly performed in the hydrophilic solvent to form a carbon nanomaterial on the surface. A radical derived from a solvent capable of bonding OH groups is generated in the solvent, and the carbon nanomaterial is made hydrophilic by the radical so that it can be dissolved in the solvent, and at the same time, stably dispersed in the hydrophilic solvent. This is a method for soluble carbon nanomaterials, and it is possible to easily dissolve poorly soluble carbon nanomaterials such as single-walled carbon nanotubes and single-walled carbon nanohorns in hydrophilic solvents. In addition, the dispersibility of the carbon nanomaterial can be stably maintained over a long period of time. In addition, it is possible to realize soluble properties that do not cause structural deterioration of the carbon nanomaterial, and it is possible to improve only dispersibility.

Example

[Example 1]

Hereinafter, the method for dissolving the carbon nanomaterial in Example 1 of the present invention will be described. In this specification, CNTs, carbon nanohorns, fullerenes, carbon nanocapsules, and the like are targeted, and the force of carbon nanomaterials may include micron-sized materials. Therefore, carbon nanomaterials including such cases are called. Further, in Example 1, as an example of the carbon nanomaterial, a multilayer carbon nano material is used. The ability to explain the case of soluble tubes (MWCNT) soluble in single-walled carbon nanotubes (SWCNT), fullerenes, carbon nanocapsules, etc. The following explanation is not limited to multi-walled nanotubes. . In addition, Example 23 will explain in detail the solubility method for further promoting the solubility property of SWCNT and single-walled carbon nanohorn (SWCNH).

[0033] Fig. 1 is an explanatory diagram of a soluble cake device according to Embodiment 1 of the present invention, Fig. 2 is a light emission image photograph of pulse discharge according to the present invention, and Fig. 3 is an output of pulse stream discharge according to Embodiment 1 of the present invention. Fig. 4 (a) is a photograph of the suspension before the pulse stream discharge process in Example 1 of the present invention, and Fig. 4 (b) is the burst discharge process in Example 1 of the present invention. Fig. 5 (a) is a photograph of the subsequent suspension, and Fig. 5 (a) is an explanatory diagram of the transmittance before and after the pulse stream discharge process and the ultrasonic dispersion process in Example 1 of the present invention. Figure 6 (a) is an SEM photograph of the multi-walled nanotube before the pulse discharge process in Example 1 of the present invention, and Figure 6 (b) is Example 1 of the present invention. SEM photo of multi-walled carbon nanotubes after pulse stream discharge treatment in Fig. 7 shows Example 1 of the present invention. Multi-layer force before and after pulse treatment Discharging treatment explanatory diagram of FTIR measurement results for single-bonn nanotubes, Fig. 8 is an emission spectrum measurement diagram of pulsed discharge force in Example 1 of the present invention, and Fig. 9 (a) is Example 1 of the present invention. FIG. 9 (b) is an enlarged explanatory view of the multi-walled carbon nanotube in FIG. 9 (a), and FIG. 10 is a pulse-stripe discharge process in Example 1 of the present invention. It is a Raman spectroscopic measurement figure of a subsequent multi-walled nanotube.

[0034] In Fig. 1! /, 1 is a hydrophilic solvent such as water, ethanol, methanol, etc., carbon nanomaterials such as CNT, fullerene, carbon nanocapsule, etc., and in Example 1, multi-walled carbon nanotubes ( The following is a suspension mixed with MWCNT), and 2 is a discharge vessel such as a discharge tube that can contain the suspension 1 and discharge inside. If the suspension 1 is not stirred before the pulse stream discharge treatment, the MWCNT settles in a short time and forms two layers.

[0035] High purity of MWCNT mixed in Suspension 1 is desirable In Example 1, 25 mg of MWCNT with a purity of 95% was suspended in lOOmL of ion-exchanged water, and thus 250 μg / mL The suspension 1 was measured, and about 10 mL of the suspension 1 was accommodated in the discharge vessel 2, and the needle-to-plate electrode described below was immersed in the suspension 1 and measured. Any method for increasing the purity of MWCNT may be used as long as it does not interfere with the subsequent discharge treatment.

[0036] 3 is a needle electrode for causing pulse streamer discharge constituting the needle-to-plate electrode, and 4 is a flat plate electrode arranged facing the needle electrode 3. The tip of the needle electrode 3 is a fine spherical body. In Example 1, it is made of tungsten and has a radius of curvature of about 0.3 mm. The flat plate electrode 4 is a stainless steel disc having a diameter of 10 mm, and the needle electrode 3 and the flat plate electrode 4 are provided with a gap length of 10 mm as a gap length g. The gap length g is preferably about 5 mm to 50 mm. That is, if the gap length g is too short, the process proceeds to arc discharge, and if it is too long, the stream discharge does not occur. Therefore, in order to generate the desired radical by generating a streamer discharge, a suitable one from 5 mm to 50 mm may be selected in consideration of the influence of the voltage and pulse width. When a high voltage is applied between the needle-to-plate electrode, a pulse streamer discharge is generated between the needle electrode 3 and the plate electrode 4. In Example 1, pulse streamer discharge is performed by a combination of the needle electrode 3 and the flat plate electrode 4 opposed to the needle electrode 3. However, in order to generate the pulse streamer discharge, it is sufficient to form a high electric field region in water. In addition to the electrodes, it is also preferable to use fine wires or wire electrodes.

[0037] Next, 5 is a DC power supply unit capable of varying the voltage, 6 is a pulse generating unit, and 7 is a gap switch having a spark gap. The DC power supply 5 is grounded at one end and connected to the pulse generator 6 at the other end to apply a negative voltage. Note that the polarity of the voltage may be positive! / !, but the conditions (voltage amplitude, pulse width, etc.) that cause stable generation of the Nord Streamer discharge may change depending on the polarity of the voltage. In this respect, in order to generate radicals, it is better to apply a negative voltage. The pulse generator 6 for the pulse streamer discharge preferably uses a Bloom line type pulse generation circuit, and this circuit has a stage having characteristics of capacitance C and inductance L per unit length in the line direction. It is expressed as an equivalent circuit distributed in multiple stages. The pulse generation unit 6 of Example 1 performs pulse streamer discharge by this Bloom line type pulse generation circuit. The force pulse generation unit 6 can bond OH groups to the surface of the carbon nanomaterial in the solvent. This produces a unique radical for solvent-derived hydrophilization. Therefore, OH groups can be bonded to carbon nanomaterials directly or through a process by reaction, and as a result, aggregates of CNTs can be loosened and repeatedly dispersed into individual CNT bundle units (in other words, fibrous CNTs). It is not limited to those using this blue mine type pulse generation circuit.

In Example 1, a coaxial cable having a length of 30 m and a characteristic impedance (LZC) ^1/2 of 55 Ω was used to configure a Bloom line type pulse generation circuit. When the gap switch 7 is operated, a voltage wave is formed at each stage and is superimposed and propagated to output a rectangular wave pulse voltage to the load side of the bloom line type pulse generation circuit. At this time, the polarity of the generated pulse voltage is opposite to the polarity of the voltage generated by the DC power supply unit 5. That is, in Example 1, the polarity of the streamer discharge is positive. The pulse width τ of the rectangular wave at this time is τ = 21 (LC) ^1/2 . This 1 indicates the length of the coaxial cable and corresponds to the number of stages in the equivalent circuit. Therefore, the pulse width τ can be controlled by adjusting the length of the coaxial cable. The radical generation rate can be controlled by controlling the pulse width τ.

[0039] In the solubilizer shown in Fig. 1, R is a charging resistance of 5Ω, and R is impedance.

1 2 A 150 Ω resistor provided for dance matching. Further, in the fusible device of Example 1, the DC power source 5 was set to −40 kV, the spark gap was set to 13 mm, and the repetition frequency was 15 Hz (pps). At this time, the theoretical pulse width τ is 329 ns.

[0040] 8 is a voltage measuring unit using a high voltage probe for measuring the output voltage, and 9 is a current measuring unit using a Rogowski coil or the like for measuring the output current of the pulse streamer discharge. Next, 10 is a control unit that controls the voltage of the DC power supply unit 5 and the repetition frequency of the pulse streamer discharge based on the measurement results of the voltage measuring unit 8 and the current measuring unit 9. 11 is a timekeeping section for measuring the duration of the pulse streamer discharge, and 12 is a counter for counting the repetition frequency.

[0041] Therefore, the operation of the soluble rice bran apparatus of Example 1 will be described below. By turning on a switch (not shown), the control unit 10 raises the DC power supply unit 5 to a predetermined voltage, and applies a negative voltage from the DC power supply unit 5 to the pulse generating unit 6. Charging progresses with the capacitor component of each stage of the Bloom line type pulse generation circuit, and is released when the gap switch 7 is turned on. A voltage wave is formed at each stage for electricity, and is superimposed and propagated to output a predetermined high pulse voltage to the needle-to-plate electrode on the load side, thereby generating a pulse streamer discharge.

[0042] This pulse streamer discharge forms plasma in water (partially gasified)

1S This plasma is a non-equilibrium plasma in which only the electron temperature is high, unlike the thermal plasma (plasma in which the electron temperature, ion temperature, and molecular temperature are all high) generated by arc discharge. Therefore, in Example 1, the water temperature can be activated at room temperature, and OH groups are bound to the surface of carbon nanomaterials such as O, 0, H, OH, and H 2 O in water.

3 2 2

The kind of radicals that can be combined can be generated. The same is true for other hydrophilic solvents such as alcohol, although the amount produced is different. This non-equilibrium plasma is difficult to generate with thermal plasma, making it possible to generate radicals. In order to generate a pulse streamer discharge that generates radicals that change the poor solubility of CNT in a soluble manner, the rise between the electrodes is several tens to several hundreds ns, and the pulse width at which the peak value is obtained is preferably 10 ns or more. Therefore, a high pulse voltage of about 1 μs or less should be applied. The upper and lower limits of the pulse width are determined for the following reasons. In other words, a time delay is unavoidable until the streamer discharge occurs after the applied voltage reaches a predetermined value. For this reason, the minimum width necessary for the discharge is that the pulse width is longer than this time delay. On the other hand, if the pulse width is too long, the streamer discharge shifts to arc discharge, causing melting of the electrode metal and the resulting contamination of the carbon nanomaterial. In order to change only the sparingly soluble property to the soluble property on the condition that the carbon nanomaterial is not affected, it is extremely important that the norm width is 1 μs or less of the predetermined length. In addition, the repetition frequency is preferably selected from lHz (pps) to 100 Hz (pps) in order to generate radicals and enhance solubility. In addition, when a hydrophilic solvent such as ethanol or methanol other than water is used as a solvent, radicals are similarly generated. The discharge time should be at least 1 minute, preferably 10 minutes to 1 hour, or even longer.

FIG. 2 is a photograph of the light emission image of this pulse streamer discharge, and FIG. 3 shows the output voltage and current waveform of the pulse streamer discharge of Example 1. According to FIG. 3, the pulse width of the fusible device of Example 1 is 353 ns, which is almost equal to the theoretical value of 329 ns. Also stand up While the pulse voltage is applied after force S, the output current increases in proportion to time. Therefore, it can be seen that the pulse streamer discharge occurred during the 200 ns when this current increased. In Example 1, radicals can be generated in the water by repeatedly performing the force streamer discharge that performs the pulse streamer discharge with a constant pulse width. Therefore, the discharge is not limited to such a pulse streamer discharge.

[0044] Next, the dispersibility of the suspension subjected to pulse streamer discharge in water will be described.

In order to evaluate dispersibility, the transmitted light intensity measurement and SEM observation of the suspension were performed on the suspension which was subjected to the pulse streamer discharge for 5 hours with the soluble cake apparatus of Example 1. A He-Ne laser (caliber: about 4 mm) was used to measure the transmitted light intensity. For SEM observation, a real surf s-view microscope (VE-7800 manufactured by Keyence Corporation) was used. The observation was performed after dropping the suspension after the pulse stream discharge treatment onto the cover glass and evaporating the water. In order to investigate the reason for the soluble melt, the absorption spectrum of the suspension after the pulse streamer discharge treatment was measured, and the emission spectrum of the pulse streamer discharge was measured. The absorption spectrum was measured using a Fourier transform infrared spectrophotometer (FTIR) (FT / IR — 620, manufactured by JASCO Corporation). The emission spectrum was measured using a spectroscope (Usio Electric Co., Ltd.). US R—40V) was used. In order to investigate whether the pulse streamer discharge affected the structure of MWCNT, after evaporating water from the suspension, the crystal was measured by a laser Raman spectrophotometer (NRS-2000 manufactured by JASCO Corporation). Sex was evaluated.

4 (a) and 4 (b) show the state of the suspension before and after the pulse streamer discharge treatment. Even if the suspension before the pulse streamer discharge treatment is mixed, MWCNT immediately precipitates as shown in Fig. 4 (a), and the supernatant aqueous solution becomes transparent. On the other hand, when the pulse streamer discharge was performed in this suspension for 5 hours, the color of the solvent gradually became black over time and the turbidity spread throughout. Even after 5 days from the end of the pulse streamer discharge, the dispersibility of the suspension was maintained in this state as shown in Fig. 4 (b). Although not shown, this dispersibility remains the same even after one month. From this result, it can be said that the pulse streamer discharge is effective for making CNT soluble in water, and in a sense, such a property was imparted to CNT. For reasons that will be described later, carbon nanomaterials such as fullerenes other than CNT, carbon nanocapsules, etc., which are not only CNT, are soluble in hydrophilic solvents, and are stable over a long period of time. It can be kept in a state dispersed in a solvent.

[0046] Next, the result of measuring the transmitted light intensity of the suspension will be described. In FIG. 1, the lateral force of the translucent discharge vessel 2 was measured by irradiating the suspension 1 with a He—Ne laser to measure the intensity of the transmitted light and the light transmittance. Figures 5 (a) and 5 (b) show the light transmittance of the suspension before and after the pulse streamer discharge treatment, and three types of transmission when ultrasonic dispersion treatment (500 W, 5 hours) is performed for comparison. Indicates the rate.

[0047] In the case of the suspension before the pulse streamer discharge treatment, since the transmittance is always 100% from the start of measurement, it can be seen that the dispersibility of MWCNT is extremely low (does not dissolve). As shown in Fig. 5 (b), the suspension of MWCNT dispersed with ultrasonic waves reached a transmittance of almost 100% in about 3 minutes, and the supernatant became transparent. In contrast, the MWCNT suspension after the pulse streamer discharge treatment had a transmittance of 5% or less even after 1 week from the start of the measurement, and the aqueous solution dispersibility was maintained. Although not shown in Figs. 5 (a) and (b), the suspension of MWCNT after the pulse streamer discharge treatment is 1 from the end of the pulse streamer discharge as described in connection with Fig. 4 (b). Even after more than a month, the dispersibility was stably maintained in water at room temperature.

[0048] Therefore, also from the viewpoint of measuring the transmitted light intensity, it can be seen that the pulse streamer discharge can dissolve the carbon nanomaterial in the hydrophilic solvent and disperse it in the solvent for a long period of time.

[0049] Here, the results of SEM observation of the MWCNT in the suspension before and after the pulse streamer discharge treatment will be described. Figures 6 (a) and 6 (b) are SEM observation results of the suspension before and after the pulse streamer discharge treatment. These SEM images were taken after evaporating the water in the MWCNT suspension. Fig. 6 (a) shows the suspension before the pulse streamer discharge treatment, and the particles are not uniformly dispersed in the solvent and round aggregated particles are observed. An enlargement of this particle is the upper right photo, which is an aggregate of MWCNT rounded with an average diameter of about 20 m. In the suspension, only such aggregates of MWCNT were observed as a whole, and dispersed MWCNTs in a dispersed state (generally in bundle units) were not observed.

[0050] On the other hand, after the pulse streamer discharge treatment, the fibrous MWCNTs are almost uniformly dispersed as shown in FIG. 6 (b). Aggregates as shown in Fig. 6 (a) It hardly exists in the aqueous solution after treatment, and is uniformly dispersed in the state shown in Fig. 6 (b)! Therefore, it can be seen that the Rustri discharge forms aggregates and stabilizes, loosens the MWCNT, and makes each fibrous MWCNT stably exist in water and disperse almost uniformly in the aqueous solution.

[0051] Thus, according to the method for soluble carbon nanomaterials of Example 1, the ability to stably disperse MWCNTs in water by pulsed strip discharge enables this soluble property to be achieved. Explain why. First, the biggest reason that pulse stream discharge contributes to this solubilization is considered to be that OH group is bonded to MWCNT by pulse stream discharge treatment. Figure 7 shows the results of FTIR measurement of the MWCNT suspension before and after the pulse stream discharge treatment. According to FIG. 7, only after Parususutori discharge treatment, contact the area of 3200cm- ¹ 3500 cm ^_1!, Absorption spectrum Te is generated! /, Ru.

[0052] This region is a force known to be an absorption spectrum due to O-H stretching vibration. Absorption in this region is due to the presence of OH fundamental force pulse stream discharge that did not exist before the pulse stream discharge treatment. This means that it is bound to MWCNT. This state is shown in Fig. 9 (b). As shown in Fig. 9 (b), a number of hydrophilic OH groups are formed in a part of MWCNT, which is inherently nonpolar (hydrophobic), and this is compatible with the hydrophilic group (OH group) of the hydrophilic solvent. It is possible to exist stably in water and is considered soluble. In other words, hydrophilic solvents such as water and organic solvents (alcohol, acetic acid, etc.) are highly hydrophilic, so they do not dissolve nonpolar solutes and easily dissolve highly hydrophilic polar solutes. On the other hand, it is thought that the OH group was bound by the pulse stream discharge and became soluble.

[0053] The following reaction can be considered as a mechanism for bonding OH groups to the MWCNT. In the emission spectrum of FIG. 8, the peaks of Ha radical (656η) and Ο radical (777nm) are clearly detected under the conditions of Example 1 (pulse voltage, pulse width, repetition frequency, discharge time, etc.). First, the O radicals generated by the discharge acidify the surface of the MWCNT, which causes the surface modification of the MWCNT, and then the H radicals generated by the discharge and the O radicals adsorbed on the surface of the MWCNT It is thought that the reaction produced OH groups. [0054] In addition, although not clearly detected in the measurement shown in Fig. 8, it is known that the pulse streamer discharge in water generates OH radicals (309nm) as described in Non-Patent Document 3 described above. ing. Therefore, in Example 1, by changing the discharge conditions, OH radicals are generated in addition to H radicals and O radicals, or OH radicals are mainly generated directly and bonded to MWCNT to form OH groups. Can do.

[0055] In addition, the second reason that the pulse streamer discharge contributes to the solubility is considered to be the presence of physical forces such as shock waves and ultrasonic waves generated by the pulse streamer discharge. When the light emission image as shown in FIG. 2 is visually observed, it can be visually confirmed that MWCNT aggregated by shock waves, ultrasonic waves, etc. are crushed into finer aggregates in the state shown in FIG. 9 (a). . It is also preferable to apply shock waves, ultrasonic waves, etc. as physical force (grinding force) externally (spontaneously) in addition to the action of the North Streamer discharge (spontaneous action).

[0056] Thus, according to Example 1, radicals such as H radical, O radical, and OH radical are generated in a hydrophilic solvent by Nord streamer discharge, and these are bonded to the carbon nanomaterial. The carbon clusters are hydrophilized and dissolved in a hydrophilic solvent. At the same time, aggregates in which carbon nanomaterials are entangled with each other by physical forces such as shock waves and ultrasonic waves generated simultaneously with the generation of radicals are separated. The material can be stably soluble in a hydrophilic solvent.

[0057] Finally, the effect of pulse streamer discharge on the structure of the carbon nanomaterial will be described. The influence of discharge on the structure of the carbon nanomaterial of Example 1 was measured by Raman spectroscopy. Figure 10 shows the results of Raman spectroscopy measurement of MWCNT. According to Fig. 10, two characteristic peaks of CNT appear before and after the no-streamer discharge treatment. The first peak is D band by amorphous carbon near 1350 cm ^_1. The second peak is the G band derived from graphite near 1590 cm- ¹ . The crystallinity of CNT can be evaluated from the ratio GZD of the heights of the D and G bands. In general, if the GZD ratio is large, it can be said that the substance has good crystallinity.

[0058] Therefore, when the GZD ratio of the MWCNT before the pulse streamer discharge is obtained based on the measurement result in the upper part of Fig. 10, the GZD ratio before the nor- mer streamer discharge is 0.7, and based on the measurement result in the lower part. The GZD ratio after the pulse streamer discharge is 0.8, which is the pulse streamer discharge. The GZD ratio was almost the same before and after the electricity. This indicates that no structural degradation of M WCNT has occurred due to the Nord Streamer discharge, so that the pulse streamer discharge has achieved solubilization without causing the structural degradation of MWC NT, and only the dispersibility has been improved. I understand that.

[0059] As described above, the soluble solvent method of Example 1 uses a streamer discharge in a suspension, so that the soluble nanomaterial in the hydrophilic solvent of the carbon nanomaterial can be easily obtained. realizable. The dispersibility of the carbon nanomaterial by this method is stably maintained over a long period of time. In addition, streamer discharge can realize solubilization without causing structural deterioration of the carbon nanomaterial, and can improve only dispersibility.

[0060] Further, the method for dissolving the carbon nanomaterial of Example 1 can uniformly dissolve the carbon nanomaterial in the hydrophilic solvent. Compared to devices that perform arc discharge or devices that separate streamer discharge in gas and dispersion processing, simple devices are required, so that soluble soot treatment can be performed at low cost and processing control is easy. .

[0061] Then, if the streamer discharge is changed to a pulse streamer discharge, the apparatus becomes extremely simple, the carbon nanomaterial can be easily and reliably dissolved in the hydrophilic solvent, and the dispersibility can be stably dispersed over a long period of time. Can be maintained.

[Example 2]

Hereinafter, the method for dissolving the carbon nanomaterial in Example 2 of the present invention will be described. In Example 2, as a carbon nanomaterial, the property of poor solubility is stronger than that of multi-walled carbon nanotubes (MWCNT)! Single-walled carbon nanotubes (SWCNT, hereinafter referred to as SWCT) and single-walled carbon nanohorns (hereinafter referred to as SWCH) are soluble. The case where it is necessary will be described. Needless to say, it is not limited to SWCNT and SWCNH, but can be applied to all carbon nanomaterials such as MWCNT.

[0063] Fig. 11 is an explanatory diagram of the soluble cake device according to the second embodiment of the present invention, Fig. 12 is a light emission image photograph of the pulse streamer discharge in the second embodiment of the present invention, and Fig. 13 (a) is a diagram illustrating the implementation of the present invention. Photo of suspension after pulse streamer discharge treatment performed with oxygen gas publishing in Example 2, Fig. 13 (b) is a pulse streamer discharge performed without publishing in Example 2 of the present invention. Fig. 13 (c) is a photograph of the suspension after treatment, Fig. 13 (c) is a photograph of the suspension before the pulse streamer discharge treatment in Example 2 of the present invention, and Fig. 14 is the presence and absence of publishing and absorption in Example 2 of the present invention. Fig. 15 (a) is an explanatory diagram of the spectral distribution of luminous intensity, Fig. 15 (a) is an explanatory diagram of the absorbance of the SWCNT suspension compared with the presence or absence of publishing in Example 2 of the present invention, and Fig. 15 (b) is Example 2 Fig. 16 is an illustration of the absorbance of the S WCNH suspension compared with the presence or absence of bubbling. Fig. 16 shows the time course of the absorbance of the SWCNT suspension after the underwater streamer discharge treatment in Example 2 of the present invention. FIG. 18 is a particle size distribution diagram of a SWCNT suspension subjected to a stream discharge treatment in combination with oxygen gas publishing in Example 2 of the invention. FIG. 18 is a pulse of the single-walled nanotube suspension in Example 2 of the present invention. It is an emission spectrum distribution map in a streamer discharge.

[0064] Fig. 19 (a) is a photograph of the single-walled carbon nanotube suspension after the pulse streamer discharge treatment performed together with the argon gas publishing in Example 2 of the present invention, and Fig. 19 (b) is the present invention. Figure 20 shows a photograph of a single-walled carbon nanotube suspension after pulse streamer discharge treatment without publishing in Example 2, Fig. 20 shows the effect on absorbance of SWCNT suspension when gas publishing in Example 2 of the present invention. Figure 21 (a) is a photograph of the SWCNT suspension after underwater streamer discharge treatment without gas publishing, and Fig. 21 (b) is a discharge treatment with nitrogen gas publishing. Fig. 21 (c) shows a state after discharge treatment while performing argon gas publishing. Fig. 2 (a) shows a case where gas publishing was performed with oxygen, nitrogen, and argon. Standard Ha emission intensity Fig. 22 (b) is a comparison diagram of emission intensities with standardized emission intensity of O radicals when gas publishing with oxygen, nitrogen, and argon.

The soluble rice bran apparatus according to the second embodiment of the present invention basically has the same configuration as that of the soluble rice bran apparatus according to the first embodiment. Accordingly, since the same reference numerals as those described in the first embodiment basically indicate a common configuration, the description is given to the first embodiment and is omitted here.

In FIG. 11, 3a is a single wire made of tungsten for causing a pulse streamer discharge, and 4 is a flat plate electrode arranged facing the wire electrode 3a. The wire electrode 3a has a diameter of 60 m. The plate electrode 4 is a stainless steel 28 mm x 58 mm rectangle, and the wire electrode 3a and the plate electrode 4 have a gap length g of 13 mm. Is provided. The gap length g is preferably set to about 5 mm to 50 mm for the same reason as described above. When a high voltage is applied between the wire-to-plate electrode, a pulse streamer discharge is generated between the wire electrode 3a and the plate electrode 4 at a plurality of locations on the wire electrode 3a. The discharge container 2 of Example 2 is a box-shaped container of 60 mm (horizontal direction) X 30 mm (vertical direction) X 3 Omm (height direction).

Further, the description of the configuration of the second embodiment is continued. 13 is a gas ejection passage for introducing oxygen and inert gas into the liquid in the discharge vessel 2 and publishing, 14 is a flow control valve provided in the gas ejection passage 13, and 15 is a stirring device. Figure 12 shows the pulse streamer discharge generated between the wire and plate electrodes. DC power supply unit 5, pulse generation unit 6, gap switch 7, further voltage measurement unit 8 for measuring output voltage, current measurement unit 9 for measuring output current, timer unit 11 and counter 12 shown in FIG. Is basically the same, and the description is omitted.

[0068] The procedure for SWCNT solubility will be described. SWCNT is mixed in a hydrophilic solvent in the discharge vessel ^2, in Example 2, water is operated, and the control unit 10 is operated. First, the control unit 10 opens the flow control valve 14 to eject a publishing gas such as oxygen into the feed liquid at a constant flow rate. Furthermore, the control unit 10 operates the stirring device 15 to stir the suspension 1 so that the distribution of bubbles and SWCNTs is uniform. After that, a high voltage is applied between the wire-to-plate electrode, pulse streamer discharge is performed for a predetermined time, and the carbon nanomaterial is dissolved. In this case as well, as in Example 1, the rise between the electrodes is several tens to several hundreds ns, and the pulse width is generated in order to generate a no-striker discharge that generates radicals that change the poor solubility of CNTs to solubility. If possible, apply a high pulse voltage of 10 ns or more and 1 μs or less at 1 Hz to: LOOHz. Discharge for at least 1 minute, preferably 10 minutes to 1 hour, or even longer.

[0069] Therefore, the operation when ejected as publishing gas will be described below. The bubbling gas is oxygen. Without pulse streamer discharge, the suspension looks like the suspension in Fig. 13 (c), and SWCNT hardly dissolves. When a pulse streamer discharge is applied to this, it dissolves as shown in Fig. 13 (b). This is as described in the first embodiment. At this time, it can be seen that Suspension 1 is totally turbid and SWCNT is dissolved. The amount of water in the discharge vessel 2 is 50 ml, the mixed SMCNT is 5 mgZ50 ml, the gas flow rate is 100 mlZmin, and the treatment time (discharge time) is 10 minutes. The pulse stream at this time The SEM photo of the SMCNT before the plasma discharge treatment is almost the same as in Fig. 6 (a), and the SEM photo of the SMCNT after the pulse streamer discharge treatment is almost the same as in Fig. 6 (b). See Fig. 6 (a) and (b)!

[0070] On the other hand, FIG. 13 shows the results when pulse streamer discharge is performed while publishing oxygen.

Shown in (a). The gas flow rate is 100mlZmin and the treatment time (discharge time) is 10 minutes. The turbidity is considerably stronger than suspension 1 in Fig. 13 (b), and the color changes to a darker color (gray near black). This indicates that SWCNT is more dissolved and evenly dispersed in the solution than in the case of only discharge. The experiment was conducted under the above conditions, and the results were the same even when the force flow rate was changed from 100 mlZmin to 500 mlZmin. The same applies when bubbling over 500mlZmin.

[0071] In order to quantitatively evaluate the effect of gas publishing, ultraviolet-visible rays were irradiated, and the absorbance of suspensions when pulse streamer discharge was performed was compared depending on the presence or absence of bubbling. Figure 14 shows the relationship between the presence of publishing during pulse streamer discharge and the spectral distribution of SWCNT absorbance. According to this, the maximum absorbance is exhibited at 256 nm regardless of the presence or absence of publishing. The suspension concentration is 10 gZml in all cases. Figure 15 (a) shows a comparison of how the presence or absence of publishing affects the water solubility of SWCNT by pulse streamer discharge, using the maximum absorption light intensity at 256 nm as an index. Figure 15 (b) shows the results of a similar evaluation for a SWCNH suspension with a suspension concentration of 50 / z gZml.

[0072] Fig. 15 (a) shows a comparison of the absorbance of the SWCNT suspensions with and without publishing at a suspension concentration of 10 gZml. According to this, the direction of publishing oxygen is 1.5 times higher than that of publishing force. This indicates that the suspension of SW CNTs with oxygen publishing is more turbid. Similarly, FIG. 15 (b) shows a comparison of the absorbance of the SWCNH suspension with and without publishing at a suspension concentration of 50 gZ ml. According to this, the direction of publishing oxygen is about twice as light as that of publishing force. This indicates that the suspension of SWCNH with oxygen publishing is much cloudy. Although not shown in Figs. 15 (a) and 15 (b), the SWCNT suspension is stable and dispersible in water at room temperature even after one month (31 days) from the end of the pulse streamer discharge. Maintained. It was confirmed that the same SWCNH suspension maintained stable dispersibility in room temperature water until the 26th. Since it was confirmed that V and deviation were stable, the experiment was terminated. Therefore, pulse streamer discharge can dissolve a single-layer carbon nanomaterial such as SWCNT or SWCNH in a hydrophilic solvent and disperse it in the solvent over a long period of time.

Further, the experiment was performed by changing the measurement conditions in the configuration of FIG. That is, a wire having a diameter of 60 μm was used as the wire electrode 3a on the high voltage side, a 15 mm × 40 mm rectangular stainless steel plate was used as the plate electrode 4 on the ground side, and the gap length g was 12 mm. In this device, a suspension containing SWCNT (Aldrich 519308-250MG) of length ~ 5 μm, diameter lnm ~ 2nm (bundle diameter 15nm), purity 50% ~ 70%, suspension concentration 100 μgZmL Pulse streamer discharge was performed for 1 hour while publishing oxygen gas in liquid 60ML. Figure 16 shows the result. Figure 16 shows the time course of the absorbance of the SWCNT suspension after the underwater stream discharge treatment. According to this, it can be seen that the absorbance peak slightly decreased for several days after the discharge treatment regardless of the presence or absence of oxygen publishing, and a part of the water-contained SWCNT reaggregated slightly. However, the absorbance of both suspensions has remained almost constant after 10 days. The reason why it is possible to maintain the soluble property for a long time is the effect of the pulse stream discharge. The rate of decrease in absorbance over 10 days is approximately 15% when oxygen publishing is performed and approximately 40% when oxygen publishing is not performed. It can be seen that reaggregation can be suppressed.

FIG. 17 compares the particle size distribution of SWCNT aggregates in a SWCNT suspension subjected to streamer discharge treatment using oxygen gas publishing. According to this, the particle size distribution is reduced by about 10 ^_2 ～10_ ³ by the discharge treatment. The SWCNT particle size after the discharge treatment is about 100ηm, which is larger than the SWCNT bundle diameter of 15nm. This is considered to be a uniform distribution even in individual bundle units.

FIG. 18 is a light emission spectrum distribution diagram during pulse stream discharge of the SWCNT suspension.

According to Fig. 18, the H a (656nm) radical, H j8 (4 86 nm) Radical intensity of 0 (777 nm) radicals Oxidation of oxygen gas is almost twice as high as that of Ha radicals, H β radicals, and Ο radicals without publishing. It can be seen that the radicals and radicals are greatly increased.

[0076] From the above, it can be seen that publishing contributes not only to a physical stirring effect but also to a chemical reaction. That is, in the vicinity along the discharge channel, there are microbubbles formed by publishing only by the microbubbles generated by the discharge, and within these microbubbles, the mean free path of the electrons in the gas (mean free path) ) Will form longer energetic electrons than that in the liquid, and this collision will produce, for example, H 0 → 11 lasers.

It is thought to generate radicals like 2 dicar + OH radicals. However, the amount of radicals varies depending on the type of bubbling gas. According to Non-Patent Document 4, when the publishing gas is oxygen, a large amount of OH radicals are generated, and when the publishing gas is argon, there are many H radicals and O radicals, and the amount of OH radicals generated is small. Forces described later in connection with Figs. 20, 22 (a), (b), and (c) Argon gas publishing has the best effect on the solubility of SWCNT. This indicates that in the case of argon, mainly generated H radicals and O radicals play a major role in soluble matter. In other words, at the time of publishing, the type of gas (actually the solubility of the gas) also has an effect, and argon shows that radicals produced by a highly soluble gas make a large contribution to OH group bonding. .

[0077] In the case of oxygen gas, it is possible that the Norse streamer discharge in water directly generates OH radicals, and this OH radical force binds to the surface of SWCNT or SWCNH to form OH groups. It is thought to be the main cause. However, in addition to this, the surface of O radicals generated by electric discharge, O force WCNT, and SWCNH are oxidized, and surface modification is thereby performed.

Three

The subsequent generation of H radicals generated by discharge reacts with O radicals or O adsorbed on the surface of SWCNT or SWCNH to form OH groups, which also contributes to solubilization.

Three

It is thought. Therefore, it may be bagged with ozone (o) gas.

Three

[0078] In this regard, as described above, when the publishing gas is an inert gas such as argon gas, in other words, when these gases generate a small amount of OH radicals, H radicals and O radicals are generated. This O radical oxidizes the surface of SWCNT and SWCNH and releases them. The H radical force generated by electricity reacts with O radicals adsorbed on this surface to generate OH groups. At this time, since it is inactive, it does not affect the electrode or the like. Since air also consists of oxygen and inert nitrogen gas, it can be understood from the above explanation as a sum. FIG. 19 (a) is a photograph of the single-walled carbon nanotube suspension after the pulse streamer discharge treatment performed together with argon gas publishing in Example 2 of the present invention, and FIG. 19 (b) is in Example 2 of the present invention. It is a photograph of the single-walled carbon nanotube suspension after the pulse streamer discharge treatment performed without bubbling. According to Figs. 19 (a) and 19 (b), it can be seen that the highest suspended state is maintained when publishing the inert gas argon. SWCNT suspension concentration 100 μg / mU Argon gas flow rate 100 mlZmin, treatment time (discharge time) 10 minutes.

FIG. 20 shows the effect of SWCNT suspension on absorbance when gas publishing anoregone and nitrogen as inert gas, that is, gas dependence of solubilization efficiency. For comparison, the absorbances without gas publishing and with oxygen publishing are also shown. Measured with a suspension of SWCNT (Aldrich 51 9308-250MG) with a 15 mm x 40 mm flat plate electrode 4 and a gap length of 12 mm as described above, and the peak absorbance after 5 days of treatment as an index without gas publishing It is a standardized and quantified value. This indicates that the effect of gas publishing is greater in the order of argon, nitrogen, and oxygen. In particular, when argon gas bubbling is used in combination, the absorbance rises more than 3 times that without publishing, that is, solubilized SWCNTs increase.

[0080] Figures 21 (a), (b), and (c) show the state of the SWCNT suspension after the underwater streamer discharge treatment, and Figure 21 (a) shows the underwater streamer discharge treatment without gas publishing. Fig. 21 (b) shows the state after the underwater streamer discharge treatment with nitrogen gas publishing, and Fig. 21 (c) shows the state after the underwater streamer discharge treatment with argon gas publishing. The effectiveness of gas publishing can be seen at a glance. In this way, SWBN by underwater streamer discharge is achieved by gas publishing of inert gas such as oxygen, argon, and nitrogen.

It can be seen that the solubility of T can be improved with high efficiency. As described above, air is a mixed gas of oxygen and nitrogen, and this is the same. In short, all gas publishing is thought to increase the radicals generated by the underwater streamer discharge and promote the modification of the SWCNT surface. The same applies to SWCNH and the like. Figure 18 shows the generation of radicals. The emission intensity of the H a (656 nm) and 0 (777 nm) radicals is 1.6 times, respectively, derived from a solvent, for example, when oxygen publishing and underwater streamer discharge are performed. 1. Increased 7 times. The emission intensity of H | 8 (486nm) and 0 (844nm) radicals also increases by 1.5 and 1.2 times, respectively.

[0081] Figures 22 (a) and (b) show the standardized emission intensity of Ha and O radicals when gas publishing is performed with oxygen, nitrogen, and argon, with the emission intensity without gas publishing as an index. It has become. In addition, the emission intensity is shown when the underwater streamer discharge is performed for 1 minute while publishing these gases and then the underwater streamer discharge is performed without publishing. The latter is slightly lower than the former, but increases at least 1.5 times more than without gas publishing. The maximum is about 3 times for argon, about 2.2 to 2.5 times for nitrogen, and about 1.6 times for oxygen. In FIGS. 22 (a) and 22 (b), the display width shown in an I shape at each light emission intensity apex shows the fluctuation range of the measurement. Therefore, the generation of Ha and O radicals is most effective by argon gas publishing, followed by nitrogen gas bubbling and then oxygen gas publishing. Similarly, the fusible efficiency shown in Fig. 20 is in the order of gas publishing of argon, nitrogen, and oxygen, which means that the radicals generated by gas publishing are closely related to the soluble qualities of SWCNT. Show that you are involved.

[0082] As shown in FIGS. 22 (a) and 22 (b), since the O radicals are increased by the inert gas and the H radicals are also increased, the gas atoms supplied for publishing are increased. It is unlikely to be a direct radical source. Furthermore, in Fig. 22 (a) and (b), when the water streamer discharge is performed for 1 minute while gas bubbling, and then the publishing is stopped and the water streamer discharge is performed under water, the emission intensity increases. It can be seen that the physical action of publishing does not work after a minute, and that the gas dissolved in water by gas publishing promoted the generation of radicals. The solubility of argon in water lcm ³ (20 ° C) is 0.035 cm ³ , the solubility of oxygen in water lcm ³ (20 ° C) is 0.031 cm ³ , and nitrogen in water lcm ³ The solubility (20 ° C) of 0.016 cm ³ strongly suggests the involvement of gas solubility. If the radicals generated by such highly soluble gases make a large contribution to the OH bond, oxygen can be OH radicals, argon and nitrogen, etc. This inert gas mainly generates H radicals and O radicals, so the combined strength of the solubility and the reaction process of the OH group may determine the degree of solubility. At least, the effectiveness of argon gas publishing is outstanding.

[0083] As described above, the solubilization method of Example 2 does not publish the gas in the suspension, and does not publish the gas. It can be dissolved in a hydrophilic solvent. The dispersibility of the carbon nanomaterial by this method is stably maintained over a long period of time. In addition, this method can achieve a soluble property that does not cause structural deterioration of the carbon nanomaterial, and can improve only the dispersibility. Further, by using a combination of streamer discharge and publishing, it is possible to suppress the subsequent re-aggregation as well as to increase the concentration of the soluble carbon nanomaterial, and to maintain the dispersibility for a long time.

[0084] In addition, since only gas publishing is performed for streamer discharge, it is simpler than an apparatus that performs high-voltage pulse arc discharge or an apparatus that separates streamer discharge and dispersion processing in gas. The equipment can be used, so that soluble soy can be processed at low cost, and control of the process becomes easy.

[0085] (Example 3)

Hereinafter, a method for dissolving the carbon nanomaterial in Example 3 of the present invention will be described. As in Example 2, Example 3 describes the case of solubilizing single-walled carbon nanotubes (SWCNT) and single-walled single-bonn nanohorns (SWCNH). Needless to say, the present invention is not limited to SWCNT and SWCNH, but can be applied to carbon nanomaterials such as MWCNT.

[0086] In Example 2, publishing was performed in order to dissolve poorly soluble carbon nanomaterials such as SWCNT and SWCNH. In contrast, in Example 3, in order to generate OH groups on the surface of SWCNT or SWCNH, an underwater streamer discharge is performed in a solvent that easily generates OH radicals.

That is, in Example 3, the suspension was made into an aqueous solution of hydrogen peroxide (H 2 O 2) and

twenty two

Perform pulse streamer discharge. At this time, the vicinity of the discharge channel is HO rich.

2 2 State. In this state, the plasma power of the pulse streamer discharge is strong, ultraviolet rays are emitted, Activate nearby HO along the discharge, for example, HO + hv → 20H radical reaction

2 2 2 2

Formed and decomposed into OH radicals. This OH radical is directly bonded to the surface of SWCNT or SWCNH to form an OH group. Fig. 23 (a) is a photograph of a single-walled carbon nanotube suspension after pulse streamer discharge treatment in an aqueous solution of peroxygen and oxygen in Example 3 of the present invention, and Fig. 23 (b) is a photograph of the present invention. 6 is a photograph of a single-walled carbon nanotube suspension before a pulse streamer discharge treatment in Example 3. FIG. According to Figs. 23 (a) and 23 (b), it can be seen that even when a pulse streamer discharge treatment is carried out with a hydrogen peroxide solution, it is suspended and maintained. There is no gas publishing, the suspension concentration of SWCNT is 100 gZml, the concentration of hydrogen peroxide (30%), the flow rate is 100 mlZmin, and the treatment time (discharge time) is 10 minutes. Even if the suspension is made into ozone gas O aqueous solution (ozone water),

Three

Can be formed.

[0088] In the solubilization method of Example 3, since a streamer discharge is performed by forming a hydrogen peroxide solution in the suspension, a slightly soluble carbon nanomaterial such as SWCNT or SWCNH is easily soluble in a hydrophilic solvent. You can do it. The dispersibility of the carbon nanomaterial by this method is stably maintained over a long period of time. In addition, this method can achieve a soluble property that does not cause structural deterioration of the carbon nanomaterial, and can improve only dispersibility.

[0089] In addition to streamer discharge, only hydrogen peroxide aqueous solution is used. Compared to devices that perform high-voltage pulse arc discharge, devices that separate streamer discharge and dispersion treatment in gas, etc. A simple and simple device can be used, so that soluble soy can be processed at low cost and control of the process becomes easy.

Industrial applicability

[0090] The present invention can be applied to a solubilizing method in which a carbon nanomaterial can be dissolved in a hydrophilic solvent to maintain dispersibility over a long period of time.

Brief Description of Drawings

[0091] FIG. 1 is an explanatory diagram of the soluble rice bran apparatus in Example 1 of the present invention.

[FIG. 2] Photoluminescence picture of pulse streamer discharge in the present invention

FIG. 3 is an explanatory diagram of output voltage and current waveform of pulse streamer discharge in Example 1 of the present invention. [Fig. 4] (a) Photograph of the suspension before the pulse stream discharge treatment in Example 1 of the present invention, (b) Photograph of the suspension after the pulse stream discharge treatment in Example 1 of the present invention [5] (a ) Explanatory diagram of transmittance before and after pulse stream discharge processing and ultrasonic dispersion processing in Example 1 of the present invention, (b) Enlarged view of chain line portion of transmittance in (a) [Fig. 6] (a ) SEM photograph of multilayer nanotube before Rustri discharge treatment in Example 1 of the present invention, (b) SEM photograph of multilayer carbon nanotube after pulse strip discharge treatment in Example 1 of the present invention

[Fig. 7] FTIR measurement results for multi-walled carbon nanotubes before and after the pulse stream discharge process in Example 1 of the present invention

[FIG. 8] Emission spectrum measurement diagram from pulse stream discharge in Example 1 of the present invention. [FIG. 9] (a) Explanatory diagram of dispersion of multi-walled carbon nanotubes after the Rustori discharge process in Example 1 of the present invention. ) Enlarged illustration of multi-walled carbon nanotubes in (a)

[Fig. 10] Raman spectroscopic diagram of multi-walled nanotubes after pulse stream discharge treatment in Example 1 of the present invention

圆 11] Explanatory drawing of the soluble potato device in Embodiment 2 of the present invention

FIG. 12 shows a luminescence image photograph of a pulse stream discharge in Example 2 of the present invention.

[FIG. 13] (a) Photograph of suspension after pulse stream discharge treatment performed together with oxygen gas publishing in Example 2 of the present invention, (b) Without gas publishing in Example 2 of the present invention. Photograph of the suspension after the pulse stream discharge treatment performed, (c) Photograph of the suspension before the pulse stream discharge treatment in Example 2 of the present invention

FIG. 14 is an explanatory diagram of the spectral distribution of the presence and absence of publishing and absorbance in Example 2 of the present invention. [FIG. 15] (a) An explanatory diagram of the absorbance of the SWCNT suspension compared with the presence or absence of publishing in Example 2 of the present invention. (B) Explanatory drawing of absorbance of SW CNH suspension compared with or without publishing in Example 2 of the present invention

[Fig. 16] Time course of absorbance of SWCNT suspension after underwater stream discharge treatment in Example 2 of the present invention.

FIG. 17 is a particle size distribution diagram of a SWCNT suspension subjected to a stream discharge treatment in combination with oxygen gas bubbling in Example 2 of the present invention. FIG. 18: Emission spectrum distribution diagram during pulse streamer discharge of single-walled nanotube suspension in Example 2 of the present invention

[FIG. 19] (a) Photograph of single-walled carbon nanotube suspension after pulse streamer discharge treatment performed together with argon gas publishing in Example 2 of the present invention, (b) No publishing in Example 2 of the present invention. Of single-walled carbon nanotube suspension after pulse streamer discharge treatment performed in

FIG. 20 is a comparative diagram showing the effect on the absorbance of the SWCNT suspension when gas publishing in Example 2 of the present invention.

[Fig.21] (a) Photo of SWCNT suspension after underwater streamer discharge treatment without gas publishing, (b) Photo of state after discharge treatment with nitrogen gas publishing, (c ) Photo after discharge treatment with argon gas publishing

[Fig.22] (a) Comparison of emission intensity with normalized Ha emission intensity when gas publishing with oxygen, nitrogen, and argon, (b) Gas publishing with oxygen, nitrogen, and argon Comparison of emission intensity with standardized emission intensity of O radical

FIG. 23 (a) Photograph of single-walled carbon nanotube suspension after pulse streamer discharge treatment in an aqueous solution of peroxygen and oxygen in Example 3 of the present invention, (b) Example of the present invention Photo of single-walled carbon nanotube suspension before pulse streamer discharge treatment in Fig. 3

1 Suspension

2 Discharge vessel

3 Needle electrode

3a wire electrode

4 Plate electrode

5 DC power supply

6 Pulse generator

7 Gap switch

8 Voltage measurement section

9 Current measurement section 050649 Control unit

Timekeeping section

Counter

Gas outlet

Flow control valve

Stirrer

Claims

The scope of the claims

[1] Carbon-based nanomaterials are mixed in a hydrophilic solvent, and radicals derived from a solvent capable of binding an OH group to the surface of the carbon-nanomaterial by repeatedly discharging a streamer in the hydrophilic solvent. It is produced in a solvent, and the carbon nanomaterial is hydrophilized with the radicals so that the carbon nanomaterial can be dissolved in the solvent, and is stably dispersed in the hydrophilic solvent.匕 Method.

[2] The method according to claim 1, wherein the streamer discharge is a pulse streamer discharge.

[3] The streamer discharge generates mainly H radicals and O radicals in the hydrophilic solvent, and forms OH groups in the carbon nanomaterial in the hydrophilic solvent. 2. A method for soluble carbon nanomaterials according to 2.

[4] The streamer discharge mainly generates OH radicals in the hydrophilic solvent and forms OH groups in the carbon nanomaterial in the hydrophilic solvent. Method for soluble carbon nanomaterials.

[5] The shock wave and / or ultrasonic wave is applied to the carbon nanomaterial in the hydrophilic solvent as a spontaneous or other physical force by the discharge during the discharge. A method for soluble carbon nanomaterials.

6. The method for soluble carbon nanomaterials according to claim 1 or 2, wherein the carbon nanomaterial is any one of multi-walled carbon nanotubes, single-walled carbon nanotubes, fullerenes, and carbon nanocapsules. .

[7] The solubility of the carbon nanomaterial according to claim 1 or 2, wherein the streamer discharge is performed by applying a pulse voltage having a pulse width of 10 ns or more and 1 μs or less between electrodes at a predetermined frequency.匕匕 method.

[8] A solvent in which carbon nanomaterials are mixed in a hydrophilic solvent, and a streamer discharge is repeatedly performed while a gas is published in the hydrophilic solvent to bond a base to the surface of the carbon nanomaterial. The carbon nanomaterial is characterized in that a radical derived therefrom is generated in the solvent, and the carbon nanomaterial is hydrophilized with the radical so that the carbon nanomaterial can be dissolved in the solvent and stably dispersed in the hydrophilic solvent. How to dissolve materials.

9. The method for soluble carbon nanomaterials according to claim 8, wherein the gas is any one of oxygen, ozone, and an inert gas.

[10] Carbon nanomaterial is mixed in a hydrophilic solvent in which hydrogen peroxide or hydrogen is dissolved, and streamer discharge is repeatedly performed in the hydrophilic solvent to bond OH groups to the surface of the carbon nanomaterial. A radical derived from a possible solvent is generated in the solvent, the carbon nanomaterial is hydrophilized with the radical to be soluble in the solvent, and is stably dispersed in the hydrophilic solvent. A method for soluble carbon nanomaterials.